The subject of this invention is a unit for the dehydration of sludges, particularly for purification plants.
As it is known, waters and liquids in general which come both from industrial discharges and household type wastes undergo a sequence of treatments aimed at eliminating the largest quantity possible of harmful components from them, before they are dispersed or introduced into drains or the like.
These treatments generally require initial active purification processes of a biological or chemico-physical nature to be carried out on the afore-mentioned waste liquids.
In particular, the initial chemico-physical purification processes, adapted for industrial waste liquids, use suitable coagulant or flocculant substances which favour the formation and precipitation of flocs of sludge.
The sludges obtained in this way are nevertheless still water-rich and therefore are sent to dehydrating equipment, where a treatment consisting of the expulsion of the largest quantity of water possible is carried out.
In this way, one aims to obtain a final harmful product or sludge which is as solid as possible and having a reduced volume to send directly for disposal or to subject to further treatments for elimination.
It is underlined that the reduction in the volume of the sludges obtained by means of dehydration is particularly important in order to reduce the costs of waste disposal of the solid substances obtained as residues and in particular the costs involved in moving and storing them.
Nevertheless, the existing dehydrating equipments, which permit the separation of liquid from the sludge mass, are based essentially on the use of filters able to retain the solid part and let the liquid phase pass through, and these filters, as they have been used up until now, give rise to two fundamental drawbacks; the results are modest and the dehydration times are considerable.
In fact, sludges are obtained which still contain large quantities of liquid and therefore are still extremely cumbersome.
As a result this has a negative effect both on the dimensions of the containers to be used and on the cost of the transport of the residue material obtained.
Furthermore, the operational phase of dehydration of the sludges are rather long, particularly if high percentage yield values are desired.
For example, the formation of water sludges with a percentage of dried product in the region of 20% or less in weight requires numerous days of filtration.
The productivity of current dehydration operations is therefore limited and the running costs are high.